The Detailed Design-

This includes providing detailed manufacturing instructions in the form of part drawings, assembly drawings and process instructions. Specifications of each part, components or subsystem are defined so that a manufacturer knows exactly what has to be made and how. Before such description are finally arrived at, the designer has to bring in the considerations of tolerance. Perfect accuracy cannot be achieved with any machine or process. No machine, no matter how precise, and no workman no matter how skilled, can produce two components that are exactly alike.